My advice: get a save game editor to up your stacks to 40 cards max and get a mod that reduces upkeep (either for yourself only, which is a cheat, or for all factions, which still benefits Dwarfs a lot but isn't a cheat). That will give you much more flexibility. Definitely get a nice mix of quarrelers, thunderers (you need both!) and real artillery. Don't bother with grudge throwers or really even organ guns. Get cannons; they're amazing, especially with tech upgrades, Master Engineers, and legendary lord passives. I run at least four in every army, and they do a really good job of softening up the enemy from extreme range. Don't be afraid to use your missile troops aggressively. Get your infantry stuck in and occupying the attention of as many enemy cards as possible, then aggressively flank with your missiles and pour fire into the enemy's undefended flanks (watch out for cav, obviously). If you do that, you'll also be well-positioned to provide crossfire on retreating enemies. You might not be able to run them down, but you can definitely shoot them in the back. I played Dwarfs on Very Hard my first campaign and I never lost a battle. Part of that is because I've been playing TW religiously since Medieval II, and part is because of save scumming. Don't be afraid to scum the crap out of your game.
As for campaign map, get Mount Gunbad. It has a unique Brightstone Mine that gives like 5000 income or something crazy like that, and can also have another 2000 income gold mine besides (I think). The Brightstone Mine also lets you recruit highly experienced artillery. Don't forget hero defense. Greenskins love killing your heroes and blocking your armies, try not to let them.
And don't get hung up on difficulty. If you need to drop it, do so (I did for my Empire campaign!). No one's going to judge you.